Corona discharge voltage regulator tube



ET AL 2,753,478

CURRENT-MCQOAMPS Jullly 3, 1956 J. D. M COTTER, JR.

CORONA DISCHARGE VOLTAGE REGULATOR TUBE Filed March 4, 1955 A w p F amu' W 9 +1 4 Z w 3 M j United States Patent CORONA DISCHARGE VgLTAGEREGULATOR TUB James D. McCotter, In, Philadelphia, Charles F. Schmitz,Jr., Lansdale, Ford K. Clarke, Kulpsville, and John F. McMahon, Jr.,Lansdale, Pa., assignors to Philco Corporation, Philadelphia, Pa., acorporation of Pennsylvania Application March 4, 1955, Serial No.492,206

10 Claims. (Cl. 313-484) This invention relates to voltage regulatortubes, and more particularly it relates to electric discharge tubesspecially designed for high voltage regulation.

A principal object of the invention is to provide a novel constructionof voltage regulator tube of the corona discharge kind as distinguishedfrom the type of regulator tube of the glow discharge or positive columnkind.

Another object is to provide a discharge tube for closely regulatingvery high voltages, for example those of the order of thousands ofvolts.

A feature of the invention relates to a corona discharge voltageregulator tube which has a substantially flat linear voltagecharacteristic over a wide range of current variation through the tube.

Another feature relates to a corona discharge voltage regulator tube ofthe concentric anode-cathode kind wherein the cathode and anode areaccurately and concentrically mounted within an enclosing tubular glassbulb with a minimum of spark-over danger between the cathode and anodeboth internally and externally of the tube. 9 J

Another feature relates to. a novel seal-off and exhaust tubulationarrangement for high voltage electric discharge tubes. f

A further feature relates to the novel anode and metal exhausttubulatiton and seal-otf mount for electron tubes, wherein tliei metaltubulation can also serve as the voltage supply coinductor to the anode.

A further feature relates to the novel organization, arrangement, andrelative llocation and interconnection of parts whereby etficient highvoltage corona discharge regulator tubes can be teconomicallymanufactured and assembled. g

Other features, and adrivantagesnot particularly enumerated will beapparent affter a consideration of the following detailed descriptions;and the appended claims.

In the drawing,

Fig. 1 is a plan View of .a corona discharge regulator tube according totheg'invention, with the enclosing glass bulb broken away art severalpoints to show the interior construction morerlearly;

Figs. 2, 3, a-nfd 4 are sectional views of Fig. 1 takenrespectivehaalong the lines 2-2, 33, and 4'4 thereof;

is a magnified sectional View of Fig. 1 taken yang the line 5-5 thereof;

Fig. 6 is a sectional view of the tubulation heat concentrator shown inFig. l;

1 Fig. 7 ,is a perspective view of one of the end sparkoverprotectionrings for the cathode cylinder of Fig. 1;

Fig. 8 is a characteristic curve of the tube of Fig. 1, showing therelation between the voltage at the terminals of the device as thecurrent flow through the device varies.

In certain kinds of apparatus it is extremely important that the voltageat certain points be very accurately regulated so as to be maintained ata constant value. For example, in certain kinds of color television setsone or more of the electrodes of the color picture tube must bemaintained at a steady high voltage, for example of the order of 25kilovolts. Yet, during the operation of the apparatus, the current toand from the electrode may vary as much as several hundred per cent.Therefore, ordinary gaseous glow discharge voltage regulator tubes areentirely useless for such high voltages. It has been proposed heretoforeto replace the ordinary gaseous glow regulator tube with a coronadischarge tube for voltage regulation. However, such prior tubes becauseof the complexity of their design have been limited in their usefulnessand do not lend themselves readily and economically to mass productionwith the desired degree of operating uniformity and accuracy. One of thedifiiculties in the manufacture of such tubes is that of preserving thespark-over insulation between the two electrodes so that they do notbreak down either internally or externally of the tube. In one knownconstruction of corona discharge voltage regulator tube, the cathode,which is of cylindrical metal construction, forms the major part of theenclosing envelope, and it requires sealing to a suitable glass headerat each end. Such a construction requires expensive lap or feather sealsbetween the tubular metal cathode and the glass headers. Furthermore,the cathode is completely exposed to external contact and unless thetube is inordinately long, the distance between the ends of the cathodeand the sealed-in lead wire for the anode is relatively short.

The present invention, on the other hand, provides a construction forcorona discharge voltage regulator tubes which overcomes the above notedand other disadvantages of the known constructions.

Referring to the drawing, the tube according to the invention comprisesa cylindrical glass bulb 10, of hard or lead glass tubing, for exampleof approximately 1 /2 inches outside diameter and with a Wall thicknessof approximately 0.1 inch. The opposite ends of the tubing 10 are closedby rounded or hemispherical domes ll, 12. Dome 11 may be formed as anintegral part of the tubing 10, whereas the dome 12 may be preformed asa separate member to act as a header for the anode and exhausttubulation mount to be described. The dome portion 12, after assembly ofthe mount parts thereon, is fused to the end of tubing 10, as indicatedby the numeral 13.

Vacuum-tight sealed through the lateral wall of tubing 10 is any wellknown form of contact button 14 for making electrical connection withthe cylindrical metal cathode 15. Located concentrically within thecathode 15 is an elongated cylindrical metal rod 16 which, like thecathode 15, is preferably of stainless steel. In order to maintain theanode 16 in its accurate concentric position with respect to the cathode15, it is supported at one end by means of a disc 17 of mica or similarinsulation. Preferably, the disc 17 is of polygonal shape so that itspolygonal corners are a somewhat tight fit against the inner face oftubing 1t Mica 1? has a central opening through which the anode rod 16tightly asses and the end 18 of the anode rod is rounded to reduce thechances of sparkover to the edge of the cathode .55. Rod 16 at itsopposite end is supported in its concentric position by being fittedwithin the open end of a metal exhaust tubulation 19. However, theinternal diameter of tubulation 19 is. substantially larger than theoutside diameter of rod 16, andthe tubulation 19 near its end is pressedinwardly at opposite sides as shown in the enlarged sectional view ofFig. 5, to contact the rod 16 at a plurality of points at which it iswelded to the rod. This construction leaves a plurality of ports bymeans of which the device can be evacuated through the tubulation 19 andby means of which the desired gas at the proper pressure can. be forcedinto the device.

The tabulation 19 is made of a. suitable alloy which;

is capable of being sealed in a vacuum-tight manner through the wall ofthe dome 12. For example, the tubulation 19 may be made of any wellknown and relatively cheap alloy which has substantially the samecoeflicient of expansion and contraction as that of the glass formingthe dome 12. It will be understood, of course, that the metal tubulation19 is accurately and centrally sealed through the dome 12 as a preformedunit therewith.

The tubulation 19 adjacent its inner end is formed with a constrictedportion 20, and located between the end 21 of rod 16 and the constrictedportion is a glass pellet 22 which can be heated by high frequencyinduction to its melting point so that upon cooling it flows intocontact with and seals the constricted portion 29 in a vacuum-tightmanner. We have found that in order to improve the sealing operation,while at the same time concentrating the induced heat at the constrictedregion 20, a metal heat concentrator or bafiie should be attached to thetubulation 19 adjacent the constricted portion 21). This heatconcentrator (see Fig. 6) may take the form of an annular cup-shapedmetal member 24 formed with a plurality of integral prongs 25 so thatthe member can be fitted over the tubulation 19 and the prongs can beforced into the external constricted portion 20 to hold the said heatconcentrator in place.

From the foregoing it will be seen that the mount elements 12, 19, 16,22, and 24 can be assembled as a unit prior to fusing this unit to theend of the tubing 10. Prior to assembling this unit in place the cathode15 is inserted into the tubing 10. As shown more clearly in Fig. 3, thecathode 15 is formed of two identical semi-circular stainless steelmembers 26, 27. Each of these members is formed at diametricallyopposite points with radially extending flanges 28, 29, 30, 31, whichabut against each other and are welded together throughout their length.We have found that this manner of constructing the cylindrical cathode15 lends itself to economical manufacture with a high degree ofcylindrical precision, and the abutting flanges can be so shaped that toall intents and purposes the interior surface of the cathode 15 is aperfect cylinder, free from edges or cylindrical irregularities whichwould otherwise tend to produce spark-over.

Fitted over each end of the cathode cylinder are respective roundedspark-over protecting end rings 32, 33. As shown more clearly in theperspective vieW of Fig. 7, the ring 33 for example consists of a metalring having its outer edge turned back upon itself to form a rounded lip34. The spacing between this turned-back lip 34 and the ring properprovides an annular recess to receive the end of the cathode 15, itbeing understood that the ring portion 35 is a tight fit within the endof the cathode 15. Welded or otherwise rigidly fastened to the lip 34are three equally spaced fiat metal spring members 36, 37, 33, which areadapted to engage flexibly the inner wall of the tubing 14 so as tomaintain the cathode 15 concentric with respect to the anode 16.

The spark-over protection ring 33 is of similar construction to ring 32,except that one of the spring fingers, for example the finger 39, islonger than the remaining two fingers, enabling finger 39 to engage theinwardly projecting base portion 40 of the contact button 14, thusproviding a positive metallic connection between the said button and thecathode 15. It will be understood, of course, that after the glasspellet 22 has been melted to seal 01f the device after evacuation andfilling with the desired gas pressure, the externally projecting end ofthe tubulation 19 serves as the lead-in connection to the anode 16. Itis believed that the manner of assembling of the various elements abovedescribed will be clear from the foregoing description.

It has been found that with a tube such as that described, it ispossible to maintain a substantially flat voltage characteristic at theterminals of the tube for a very great change in current through thetube. For example, as shown in Fig. 8, the tube maintains a substantialconstant value of 25 kilovolts even though the current through the tubeshould vary between 50 and 500 microamperes. In such a tube, the gasfilling was substantially pure hydrogen at a pressure of approximately40 pounds per square inch. With such a tube the rod 16 extendedapproximately 1 /2 inches beyond the left-hand end of the cylindricalcathode 15, that cathode having an internal diameter of 1.5 inches andan axial length of approximately 4.8 inches. The anode rod 16 has adiameter of approximately 0.125 inch.

Various changes and modifications may be made in the disclosedembodiment without departing from the spirit and scope of the invention.For example, while reference has been made to the anode 16 as being inthe form of a solid rod, it will be understood that it may be in theform of a cylindrical stainless steel tube, both ends of which are opento facilitate exhaustion of the envelope. In that event the tubularanode 16 may be a telescopic fit with respect to the metal tubulation19. Furthermode, in certain cases the anode 16 may be an integralcontinuation of the exhaust tubulation, thus performing a triplefunction, namely as anode, exhaust tubulation and lead-in.

What is claimed is:

1. A high voltage regulator tube of the corona discharge kind,comprising, an enclosing envelope of insulating material containing agas, a cylindrical cathode open at both ends, a cylindrical anodepassing interiorly through and extending beyond the ends of saidcathode, means sealed through the wall of said envelope for makingelectrical contact with said cathode, a rigid metal lead-in sealedthrough one end of said envelope in alignment with said anode andrigidly fastened to one end of said anode, and insulating means throughwhich the opposite end of the anode passes to maintain the anodeconcentric with the cathode.

2. A high voltage regulator tube, according to claim 1, in which theinternal diameter of said cathode and the external diameter of saidanode are correlated with the gas pressure within said envelope tostabilize the voltage applied to said cathode and anode. by coronadischarge therebetween.

3. A high voltage regulator tube of the corona discharge kind,comprising a vitreous enclosing envelope containing an ionizable gas athigh pressure, a contact member sealed through the envelope wall formaking electrical contact with said cathode, a cylindrical anodeconcentric within said cathode, at metal exhaust tubulation sealedthrough one end of {the envelope concentric with said anode and fastenedthereto, and fusible means within said tubulation for vacutjim-tightsealing of said envelope. 1

4. A high voltage regulator tulpe according to claim 3, in which saidmetal tubulation hi1 which said anode and exhaust tubulation aretelescopicailly joined while providing a plurality of exhaust ports th:rebetwcen.

5. A high voltage regulator tube according to claim 3, in which saidanode is in the form hgf a cylindrical metal tube with open ends.

6. An electron discharge tube, compili'sing an enclosing envelope closedat one end by an insulatingxheader, a plurality of spaced electrodeswithin said envelop a metal exhaust tubulation vacuum-tight sealedthrong lx said header and having one end extending into said envelopexsaid one end being fastened to one of said electrodes, said tubulationhaving a constricted region, and a fusible material located within saidtubulation adacent said constricted region to form a vacuum-tight sealfor said tubulation at said constricted region.

7. An electron discharge tube according to claim 6, in which saidconstricted region and said fusible element are located entirely withinsaid envelope and in spaced relation to the sealing-in region betweensaid tubulation and said header.

8. An electron discharge tube according to claim 7, in which saidtubulation carries adjacent said constricted region a heat concentratorfor concentrating to said constricted region the heat required forfusing said fusible material.

9. An electron discharge tube according to claim 7, in which the heatconcentrator is in the form of an annular metal flange fastened to theexterior to said tubulation adjacent said constricted region.

10. A high voltage regulator tube of the corona discharge kind,comprising an enclosing envelope having an insulating header at one end,an insulation bridge closely fitted within the end of said envelopeopposite to said 10 header, metal rod means having one end. passingthrough said bridge and the opposite end sealed through said header,said opposite end being tubular to form an exhaust tubulation, acylindrical metal cathode surrounding said rod means, means to supportsaid cathode at opposite ends against the wall of said envelope andconcentric with said rod means, and a fusible element within saidtubulation portion of said rod means to seal said tube vacuum-tight.

No references cited.

